Laser sensitometer

ABSTRACT

A laser and a negative lens are used in a sensitometer to produce a diverging beam of coherent monochromatic light which is desirable in making sensitometric test strips from lightsensitive material that is being tested for resolution response.

United States Patent Hocker et al.

[ 51 July 18,1972

[ LASER SENSITOMETER [72] Inventors: Richard L. Hocker, 1110 Birch St.,VAFB, Calif. 93437; Conrad P. Czerniejewski, 7550 Norwood Ave.,Melbourne, Fla. 32901; John D. Hopper, 1389 Stanley Lane, Melbourne,Fla. 32935 221 Filed: Oct.23, 1970 21 Appl.No.: 83,563

US. Cl. ..356/256, 95/10 R ..G0lj 1/52 Field of Search ..356/20l203,256;

[56] References Cited UNITED STATES PATENTS 2,326,007 8/1943 Capstaff..356/ 202 3,556,664 l/l971 Blaisdelletal ..356/203X PrimaryExaminer-Ronald L. Wibert Assistant Examiner-F. L. Evans Attorney-HarryA. Herbert, Jr. and Arsen Tashjian ABSTRACT A laser and a negative lensare used in a sensitometer to produce a diverging beam of coherentmonochromatic light which is desirable in making sensitometric teststrips from light-sensitive material that is being tested for resolutionresponse.

1 Claim, 1 Drawing figure Patented July 18, 1972 3,677,653

INVENTORS 2/6 #420 ,4. 114:

I ,4 r NEX'S BACKGROUND OF THE INVENTION This invention relates tophotography and, more particularly, to a sensitometer.

Sensitometers are not, per se, novel. They are well known in thephotographic art as apparatus for making sensitometric test strips fromlight-sensitive material to detemtine resolution response of thematerial. It may be fairly and accurately stated that a sensitometercomprises a light source and means for producing a graded series ofexposures of the light-sensitive material being tested. Said meansincludes a step tablet or, as more popularly known, an optical wedgewhich in turn comprises a series of screens or steps, conventionally 21,of known absorbing power. The optical wedge is held in contact with thelight-sensitive material being tested and a light of known intensity isdirected onto the optical wedge. The steps of the optical wedge areequal in that each differs in density from the preceding one by an equalamount. Each step is given the same exposure, either individually orsimultaneously. The result is a test strip of the light-sensitivematerial being tested, which is a positive of the optical wedge and fromwhich, after development, the characteristics of the light-sensitivematerial may be determined.

Light sources used in sensitometers must be reproducible in intensityand. in spectral distribution. In essence, a light source giving uniformillumination is necessary. Such light sources todate have been either ofthe incandescent type, such as a tungsten filament electric lamp, or ofthe flash type, such as an electric flash lamp. Each source has severedisadvantages. With the use of tungsten filament lamps it is extremelydifficult to control the quantity of light which is obtained and tocontrol the spectral distribution of the light. The use of flash lampsrequires complicated equipment, controls and adjustments, and does notprovide for flexibility in time duration of the flash that would enabledistribution of color balance in color film or of contrast in black andwhite film. Additionally, neither an incandescent light source nor aflash type light source can be used, even if combined with a narrow beamtransmission filter, to obtain a beam narrower, i.e. less, than Angstromunits. Further, if a beam that narrow could be obtained from a source ofwhite light, the beam would not be bright enough at a short exposuretime, e.g., l millisecond.

Our invention eliminates these disadvantages and, thereby, constitutes asignificant advance in the state-of-the-art.

SUMMARY OF THE INVENTION This invention pertains to a sensitometerwherein a laser and a negative lens forward of the laser are used as themeans for producing a divergent coherent monochromatic light beam.

Therefore, the principal object of this invention is to provide novelapparatus for making sensiometric test strips from light-sensitivematerial.

Another object of this invention is to provide apparatus which is notsubject to the disadvantages heretofore stated.

Still another object of this invention is to provide a sensitometricapparatus in which a coherent monochromatic light source is used.

Yet another object of this invention is to provide a sensitometer inwhich the light source includes a laser.

These, and other and related, objects of this invention will becomereadily apparent after a consideration of the description of theinvention and reference to the drawing.

DESCRIPTION OF THE DRAWING The drawing is a side elevation view, insimplified schematic form, of a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawing,therein is shown, in a side elevation view and in schematic form, apreferred embodiment of our invention which includes means for producinga monochromatic light includes means for emitting a beam of collimatedcoherent monochromatic light, such as laser 10, and means for divergingthe beam of collimated coherent monochromatic light, such as negativelens 20 which is suitably positioned in front of i.e., forward of, laser10.

The means for producing a graded series of exposures of thelight-sensitive material being tested includes optical wedge 30 which ispositioned in front of, i.e., forward of, negative lens 20.

Also shown in the drawing are light-sensitive material to be tested 40which is forward of, and substantially in contact with, optical wedge30; collimated coherent monochromatic light beam 50 emitted from laser10; and diverging coherent monochromatic light beam 51. The direction ofbeam 50, and of rays thereof, and of diverging beam 51, and of raysthereof, is as indicated by the arrows on the representative rays. Thedirectional designation forward or front is as indicated by the arrow inthe drawing, i.e., to the readers right.

MODE OF OPERATION OF THE PREFERRED EMBODIMENT When it is desired to makea sensitometric test strip of a light-sensitive material, thelight-sensitive material, such as 40, is placed in, or is otherwisebrought into, surface-to-surface contact with optical wedge 30.

Laser 10 is then pumped and pulsed and emits collimated beam 50, therays of which, by definition and by fact, are parallel. The beam 50, andthe rays thereof, are diverged by negative lens 20 and impinge uponoptical wedge 30. The diverged beam 51, and the rays thereof, then passthrough the steps of various density of optical wedge 30 and impingeupon the front surface of light-sensitive material 40 which is beingtested.

Light-sensitive material 40 is then developed by conventional means andthe characteristics of the light-sensitive material 40 are determined bymethods and apparatus already known in the art.

While there has been shown and described the fundamental features of theinvention, as applied to a preferred embodiment, it is to be understoodthat various substitutions and omissions may be made by those ofordinary skill in the art without departing from the spirit of theinvention. For example, a filter of the neutral density type may beinterposed between negative lens 20 and optical wedge 30 to attenuatethe energy level of divergent beam 51.

What we claim is:

1. A sensitometer for making sensitometric test strips fromlight-sensitive material being tested, comprising:

a. means for producing a diverging beam of coherent monochromatic light,which includes:

1. a laser emitting a beam of collimated coherent monochromatic light;

2. and, a negative lens for diverging said beam of collimated coherentmonochromatic light, wherein said negative lens is positioned forward ofsaid laser emitting a beam of collimated coherent monochromatic light;

b. and, means for producing a graded series of exposures of thelight-sensitive material being tested, wherein said means includes anoptical wedge and is positioned forward of said negative lens.

1. A sensitometer for making sensitometric test strips fromlight-sensitive material being tested, comprising: a. means forproducing a diverging beam of coherent monochromatic light, whichincludes:
 1. a laser emitting a beam of collimated coherentmonochromatic light;
 2. and, a negative lens for diverging said beam ofcollimated coherent monochromatic light, wherein said negative lens ispositioned forward of said laser emitting a beam of collimated coherentmonochromatic light; b. and, means for producing a graded series ofexposures of the light-sensitive material being tested, wherein saidmeans includes an optical wedge and is positioned forward Of saidnegative lens.
 2. and, a negative lens for diverging said beam ofcollimated coherent monochromatic light, wherein said negative lens ispositioned forward of said laser emitting a beam of collimated coherentmonochromatic light; b. and, means for producing a graded series ofexposures of the light-sensitive material being tested, wherein saidmeans includes an optical wedge and is positioned forward Of saidnegative lens.